ServerPilot's First Class and Business plans gives you monitoring dashboards where you can view and understands your server's memory usage.
On the Economy plan, you can use the command line to check your server's memory usage.
First, SSH in to your server as root.
Then, enter the following command:
free -m
This will show you how much memory (RAM) is present, displayed in megabytes (MB).
This will show the amounts of your total, used, and free memory.